rANmsE.  LAKE    SUPERIOR    REGION.  121 
ntiinately  associated  with  a  syeuitic  granite  which  is  a  metamorphic 
:ock,  all  stages  being  seen,  from  the  perfectly  crystalline  granite  to  the 
mchanged  sedimentary  layers.  The  Cupriferous  series  is  regarded  as 
Potsdam. 
Upham,159  in  1880,  describes  granites  and  gneisses  at  numerous  locali- 
ties in  the  Minnesota  valley.  In  the  conglomerate  opposite  New  Ulm 
ind  in  the  quartzite  at  Red  stone  are  found  numerous  pebbles  of  quartz 
md  jasper,  but  no  granite  pebbles  are  seen,  although  it  outcrops  close 
to  the  west. 
Hall  (0.  W.),160  in  1880,  describes  the  rocks  between  the  mouths  of 
Poplar  and  Devil's  track  rivers  on  lake  Superior  to  be  dark  colored 
3asic  rocks  of  igneous  origin  belonging  to  the  Cupriferous  series,  with 
:he  exception  of  a  few  beds  of  sandstone  and  conglomerate  interbedded 
mth  the  igneous  rocks.  The  Sawteeth  mountains  are  formed  as  a  re- 
mit of  combined  igneous  action  and  the  folding  of  sedimentary  strata 
md  erosion. 
Winchell  (N.  H.),161  in  1881,  gives  many  details  as  to  the  rocks  of 
lortneastern  Minnesota.  At  Pigeon  point  is  a  massive  bedded  or  jointed 
formation  like  that  at  Duluth,  with  which  it  may  be  parallelized.  The 
tatter  belongs  to  the  Cupriferous  series  and  the  former  to  the  Animikie, 
so  that  the  Animikie  appears  to  be  a  downward  extension  of  the  Cu- 
priferous. At  Mountain  lake  the  hills  are  short  monoclinals  of  gray 
luartzite,  with  beds  of  argillaceous  and  black  slate,  dipping  to  the 
southward  usually  at  an  angle  of  8°  or  10°,  and  covered  with  a  greater 
3r  less  thickness  of  trap  rocks.  In  beds  generally  less  than  50  feet, 
but  sometimes  150  feet  thick,  the  trap  and  slate  dip  together,  so  that 
bhe  hills  have  gradual  slopes  toward  the  south,  and  steep  or  perpen- 
licular  slopes  toward  the  north.  The  quartzite  must  be  an  immense 
formation,  as  it  is  seen  at  Grand  portage  and  all  over  Pigeon  point, 
ind  on  the  islands  of  the  point.  The  quartzite  formation  of  Gunflint 
lake  seems  to  graduate  downward  into  the  irony  and  carbonaceous 
Grunflint  beds.  A  greenish,  schistose,  porphyritic  rock  cut  by  veins  of 
milky  quartz  is  found  in  nearly  a  vertical  attitude  on  Gunflint  lake, 
rhis  is  supposed  to  be  the  Canadian  Huronian,  and  underlies  the 
quartzite  and  Gunflint  beds  apparently  unconformablyj  at  least,  it  is  a 
listinct  formation  from  the  Grand  portage  slates.  The  quartzite  is  locally 
i  quartzite  conglomerate.  The  Knife  lake  serpentinous  quartzite  is 
:egarded  as  Huronian.  On  the  south  side  of  Vermilion  lake  are  beds  of 
asper  and  iron  which  are  regarded  as  the  equivalent  of  the  Gunflint 
3eds.  These  are  conformable  with  the  magnesian  schists  and  slates, 
ivhich  are  in  a  vertical  attitude.  They  pass  down  into  the  schists,  and 
n  places  the  schists  and  schistose  structure  penetrate  the  jasper  and 
ron.  It  l^uggested  that  the  apparent  conformity  between  the  ferru- 
ginous beds  "aud  underlying  slates  and  schists  is  only  a  superinduced 
me,  the  original  bedding,  which  may  have  been  nearly  horizontal,  hav- 
ng  been  obliterated  by  the  change. 
